Lipoxins are a group of biologically active mediators derived from arachidonic acid through the action of lipoxygenase (LO) enzyme systems. (Serhan, C. N. and Samuelsson, B. (1984) Proc. Natl. Acad. Sci. USA 81:5335). Formation in human cell types is initiated by 5-LO or 15-LO. (Serhan, C. N. (1991) J. Bioenerg. Biomembr. 23:105). Single-cell types generate lipoxins at nanogram levels during human neutrophil-platelet and eosinophil transcellular biosynthesis of eicosanoids. (Serhan, C. N. and Sheppard, K.-A. (1990) J. Clin. Invest. 85:772). LXs are conjugated tetraene-containing eicosanoids that modulate cellular events in several organ systems.
Lipoxin A4 (LXA4) and lipoxin B4 (LXB4) are the two major lipoxins. Each enhances protein kinase C (PKC) activity in nuclei of erythroleukemia cells at 10 nM (Beckman, B. S. et al. (1992) Proc. Soc. Exp. Biol. Med. 201:169). Each elicits prompt vasodilation at nM levels (Busija, D. W. et al. (1989) Am. J. Physiol. 256:H468; Katoh, T. et al. (1992) Am. J. Physiol. 263 (Renal Fluid Electrolyte Physiol. 32):F436). The vasodilatory effects of lipoxins are well-documented. For example, administration of LXA4 in micromolar amounts via inhalation blocks bronchoconstriction in asthmatic patients. (Christie, P. E. et al. (1992) Am. Rev. Respir. Dis. 145:1281).
In the 10xe2x88x9210 M range, LXA4 also stimulates cell proliferation in combination with suboptimal concentrations of granulocyte-macrophage colony stimulating factor (GM-CSF) to induce myeloid bone marrow colony formation (Stenke, L. et al. (1991) Biochem. Biophys. Res. Commun. 180:255). LXA4 also stimulates human mononuclear cell colony formation (Popov, G. K. et al. (1989) Bull. Exp. Biol. Med. 107:93).
LXA4 inhibits chemotaxis of polymorphonuclear leukocytes (Lee, T. H. et al. (1991) Biochem. Biophys. Res. Commun. 180:1416). An equimolar combination of lipoxins has been found to modulate the polymorphonuclear neutrophil-mesangial cell interaction in glomerular inflammation. (Brady, H. R. et al (1990) Am. J. Physiol. 809). Activation of the polymorphonuclear neutrophils (PMN) includes the release of mediators of structural and functional abnormalities associated with the early stages of glomerular inflammation. (Wilson, C. B. and Dixon, F. J. (1986) In: The Kidney, edited by B. M. Brenner and F. C. Rector. Philadelphia, Pa.: Saunders, p. 800-891).
Lipoxins act as antagonists to leukotrienes (LT), which are mediators of inflammation. LXA4 modulates LTC4-induced obstruction of airways in asthmatic patients. (Christie, P. E. et al. (1992) Am. Rev. Respir. Dis. 145:1281). LXA4 inhibits LTD4- and LTB4-mediated inflammation in animal in vivo models. (Badr, K. F. et al (1989) Proc. Natl. Acad. Sci. 86:3438; Hedqvist, P. et al. (1989) Acta Physiol. Scand. 137:571). Prior exposure to LXA4 (nM) blocks renal vasoconstrictor actions of LTD4 (Katoh, T. et al. (1992) Am. J.Physiol. 263 (Renal Fluid Electrolyte Physiol. 32) F436). Leukotriene-induced inflammation occurs, for example, in arthritis, asthma, various types of shock, hypertension, renal diseases, allergic reactions, and circulatory diseases including myocardial infarction.
Although lipoxins are potent small molecules that could be administered in vivo to treat a number of diseases and conditions, these molecules are short-lived in vivo. Compounds having the same bio-activities as natural lipoxins, but a longer in vivo half-life would be valuable pharmaceuticals.
This invention features substantially purified 15-epi-lipoxin compounds. In one embodiment, the 15-epi-lipoxin compound is 15R-5,6,15-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid and in another embodiment, this acid has a 5S,6R, configuration (15-epi-LXA4). In other embodiments, the 15-epi-lipoxin compound is 15R-5,14,15-trihydroxy-6,10,12-trans-8-cis-eicosatetraenoic acid, and this acid has a 5S,14R configuration (15-epi-LXB4). In still other embodiments, the 15-epi-lipoxin compound is 15-hydroxyeicosatetraenoic acid (15-HETE), and this acid has a 15R configuration.
This invention also features lipoxin analogs, which have an active region that is the same or similar to natural lipoxin, but a metabolic transformation region which is more resistant to in vivo catabolism. The instant disclosed lipoxin analogs therefore have the biological activity of natural lipoxins, but a longer metabolic half-life. Certain of the instant disclosed lipoxin analogs may additionally have an increased in vivo potency, higher binding affinity to lipoxin receptors or enhanced bio-activity as compared to natural lipoxins.
Like natural lipoxins, the instant disclosed small molecules are highly potent and biocompatible (i.e. non-toxic). However, unlike natural lipoxins, lipoxins analogs inhibit, resist, or more slowly undergo metabolism and therefore have a longer pharmacological activity. Further, the instant disclosed compounds are more lipophilic than natural lipoxins and therefore are more readily taken up by biological membranes.
In addition, the invention features methods of ameliorating an undesired proliferation of certain cells based on contacting the cells with an effective amount of a substantially purified 15-epi-lipoxin compound. In preferred embodiments, the cells are undergoing cancerous or tumorous growth. Also in preferred embodiments, the cells are selected from the group consisting of: an epithelial cell, a leukocyte, an endothelial cell, and/or a fibroblast. In certain preferred embodiments of the invention, cells are contacted in vivo. In another embodiment, cells are contacted ex vivo.
The invention also features methods for ameliorating a cell proliferative disorder in a subject by administering an effective amount of a substantially purified 15-epi-lipoxin compound.
In another aspect, the invention features pharmaceutical compositions having the substantially purified 15-epi-lipoxin compound of the present invention and a pharmaceutically acceptable carrier. In a preferred embodiment, the 15-epi-lipoxin compound is in an amount effective to prevent an undesired proliferation of cells in a subject. In another embodiment, the pharmaceutical composition includes an effective amount of acetylsalicylic acid (ASA).